Seat belt retractors have been employed in aircraft and automotive safety installations for many years. Originally developed to perform a housekeeping task, the retractors began to perform a myriad of other functional duties beyond simply winding up surplus belting or webbing. The seat belt retractors were adapted to extend needed webbing and then lock at a selected extension or when emergency situations presented themselves. Slight retraction after withdrawal of webbing caused a locking pawl to engage a ratchet carried by the spool of a retractor as by removing a pawl blocking element. Thereafter, the retractor was said to be in an automatic lock mode since the pawl, while allowing retraction of webbing, would not allow further withdrawal until the pawl was physically separated from contact with the ratchet. It was usual to cancel the automatic locking structure by a selected amount of retraction as by a webbing follower or by a rotation sensor or clutch to shift the pawl out-of-engagement with the ratchet against a spring bias urging the pawl toward the ratchet. These devices were known as automatic locking retractors, their pawls engaging the ratchet in the locking mode in the natural course of a user's manipulation of the webbing.
Two structures in the prior art exemplify this automatic locking retractor and these are seen in the U.S. Pat. No. 3,667,698 to Robert C. Fisher and the U.S. Pat. No. 3,412,952 to G. Wohlert.
Another and even older locking type of seat belt retractor is the vehicle sensitive retractor and retractors of this type employ a sensor which relates itself to changes in velocity or acceleration and deceleration of the vehicle in which the retractor is installed. Generally, such devices utilize an inertial function of an element, like a pendulum, roller, weight or pool of electrically conducting fluid to activate either directly or indirectly a pawl which was moved (as a consequence of the inertial displacement) to lock contact with the ratchet of the retractor in prevention of webbing withdrawal. A typical early development is seen in the U.S. Pat. No. 3,960,339 to Robert C. Fisher.
Examples of further developments are seen in the work of retractor devices which provide redundant locking systems or combinations of the automatic locking mode and the vehicle sensitive locking mode in a single retractor structure as, for example, the retractor of Robert J. Rumpf in U.S. Pat. No. 4,083,512.
Recently, the work of T. Kubota, seen in U.S. Pat. No. 4,402,473, of John W. Frankila, et al in U.S. Pat. No. 4,327,882, and of Robert J. Rumpf in the U.S. Pat. No. 4,427,164, show activity looking to the selective and manual overriding of a vehicle sensitive locking system. In such instances, the selection of an automatic locking mode acts substantially directly on the lock pawl element. A similar type of device is seen in the U.S. Pat. No. 4,428,545 to Katsumi Naitoh. A cam functioning mode selecting device is found in the structure described in the patent application of Wallace Carson Higbee, Ser. No. 589,679, filed on Mar. 15, 1984.
The present invention extends and improves these directions to provide a relatively simple piloted pawl means for selection of lock mode and automatic monitored disconnect of that mode to restore a prior mode. The invention includes a self-actuating mode cancellation feature which is independent of selective operation of the means for selection of lock mode and restoration of the retractor to an inertially monitored or vehicle sensitive lock mode following selected retraction movement of the spool of the retractor.
It is the primary object of the present invention to improve on the prior conversion structures by the provision of a pilot pawl system which improves the sensitivity of the locking function in both modes and reduces the strength of the bias required to achieve the threshold of the automatic locking mode and substantially simplifies the construction of the conversion apparatus while providing a conversion available to a wider variety of plural spool constructions than those in which a more or less direct inertial actuation is required for lock or plural spools. Either mode selected causes movement of the pilot pawl and thereafter the principal pawl is driven by the webbing and monitored as it is withdrawn from the spool or as the spool senses the force.
An object of the present invention is to provide a selectively operable lock acting on a spool of webbing in a retractor in elimination of the need for excessive withdrawal of webbing from the spool and to secure infant child carriers, children, cargoes and persons to the vehicle seat in a lock mode which is automatically thereafter engaged to prevent any further webbing withdrawal. The retractor improvement of the present invention does not impede retraction of webbing.
Another object is to provide an improved selectively operable lock means which can be engaged or disengaged without necessity for complete rewind in restoration of a vehicle sensitive (inertial) locking means.
Still another object is to achieve the foregoing objects by use of a piloted pawl structure whereby it is unnecessary to engage the principal pawl directly in achievement of the selection of an automatic locking mode. The pilot pawl is mounted on the principal pawl and the driving of the pilot pawl by the withdrawal of webbing after contact of a pilot ratchet with the pilot pawl drives the principal pawl into force and lock engagement against the principal ratchet. The pilot system, operable in both lock modes, substantially extends the operability and sensitivity of the selection structure.
Another object is to provide a reversible selection means available for remote operation as by toggle-detent selection, hydraulic or pneumatic selection, the same gear-cam means used to cancel the automatic locking mode, and by electromechanical structures as, for example, a reversible solenoid means.
Other objects, including modular construction, low weight, simplicity, economy, amenability to plural and dual spool retractors, will be apparent as the description proceeds.